The asymmetric unit of the title compound, 2C8H9N2+·C10H6O6S22−, contains a 2-methylbenzimidazolium cation and one half of a naphthalene-1,5-disulfonate anion. The formula unit is generated by an inversion center. In the crystal, N—H⋯O hydrogen bonds link the components into chains along . In addition, weak C—H⋯O hydrogen bonds and weak C—H⋯π interactions are observed. The methyl H atoms were refined as disordered over two sets of sites with equal occupancy.